<wicket:panel xmlns:wicket="http://wicket.apache.org">
  <div wicket:id="feedbackul">
    <div wicket:id="messages" class="alert alert-dismissable">
      <button type="button" class="close" data-dismiss="alert" aria-hidden="true">&times;</button>
      <wicket:container wicket:id="message" >A message</wicket:container>
    </div>
  </div>
</wicket:panel>